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%I #8 Oct 03 2016 15:41:40
%S 1,0,0,0,2,0,0,0,13,0,0,0,304,0,0,0,11395,0,0,0,478444,0,0,0
%N Number of root classes of words in F_2 whose minimal words have length n.
%C F_2 is the free group on two generators.
%C a(n) = 0 if n is not divisible by 4.
%H Bobbe Cooper and Eric Rowland, <a href="http://arxiv.org/abs/0909.0561">Growing words in the free group on two generators</a>, Illinois Journal of Mathematics 55 (2011) 417-426.
%H Bobbe Cooper and Eric Rowland, <a href="https://arxiv.org/abs/1307.8216">Classification of automorphic conjugacy classes in the free group on two generators</a>, Algorithmic Problems of Group Theory, Their Complexity, and Applications to Cryptography, edited by Delaram Kahrobaei and Vladimir Shpilrain, Contemporary Mathematics 633 (2015) 13-40.
%Y A224073 is the number of all equivalence classes.
%K nonn,hard,more
%O 0,5
%A _Eric Rowland_, Mar 30 2013